1. Technical Field of the Invention
The present invention relates to an improvement in an electric connecting terminal, in which tips of at least one pair of piercing portions erected on both side edges of a plane portion of the electric connecting terminal penetrate through a coating and a conductor in a flat circuit body and then the tips is fold in such a direction as to approach each other, thereby connecting the electric connecting terminal to the flat circuit body.
2. Related Art
FIG. 9 shows a flat circuit body 1 and a related electric connecting terminal 2 to be connected to the flat circuit body 1.
The flat circuit body 1 is an FFC (flexible flat cable) which is finished to be a band-shaped cable having a flexibility as a whole by coating a plurality of elongated thin-plate shaped conductors 4a, 4b, . . . with a thin film-shaped insulating coating 5. The conductors 4a, 4b, . . . are formed by various manufacturing methods, for example, are formed by pattern printing or by sticking a preformed tape-like conductive material onto an insulating sheet.
The electric connecting terminal 2 is disclosed in JP-A-11-144780, for example, and has such a structure that a plane portion 6, a plurality of pairs of piercing portions 7 and 8 erected from opposite side edges at the base end side of the plane portion 6 and a terminal connecting portion (not shown) formed on the tip side of the plane portion 6 are integrally provided.
The terminal connecting portion (not shown) is to be connected to another connecting terminal and, for example, is formed to have a female terminal structure to be accommodated and held in a connector housing or a male terminal structure.
The electric connecting terminal 2 is a so-called piercing terminal. The tips of the piercing portions 7 and 8 provided on opposite side edges of the plane portion 6 penetrate through the coating 5 and the conductor 4a (4b) in the flat circuit body 1 and are then folded in such a direction as to approach each other as shown in FIG. 10. Therefore, the electric connecting terminal 2 is connected to the flat circuit body 1 electrically and mechanically.
Specifically, the conductor 4a (4b) of the flat circuit body 1 can be connected to the electric connecting terminal 2 by causing each of the tips of the piercing portions 7 and 8 to penetrate through the flat circuit body 1 and folding the tip without peeling the flat circuit body 1. Consequently, the number of the processing steps required for the connection can be reduced, so that a work for wiring the flat circuit body 1 can be carried out at a lower cost.
However, as shown in FIG. 10 in the electric connecting terminal 2, each pair of the piercing portions 7 and 8 is formed so as to individually have a dimension L1 required for folding the piercing portions 7 and 8 and have a clearance L2 required for avoiding an interference between the piercing portions 7 and 8 during the folding operation. Therefore an occupied width L3 in the flat circuit body 1 of one electric connecting terminal 2 becomes great.
As a result, an array pitch P1 of the conductors 4a, 4b, . . . on the flat circuit body 1 is increased. Thus, there is a problem in that the size of the flat circuit body 1 is increased.
Moreover, in the electric connecting terminal 2, the tip portions of the piercing portions 7 and 8 which are folded are returned by a spring back as shown in an arrow A of FIG. 11. As a result, there is a possibility that the fixation of the electric connecting terminal 2 to the flat circuit body 1 maybe slackened and conducting reliability may be deteriorated due to the generation of looseness.
In order to prevent the conducting reliability from being deteriorated due to such a spring back, there is proposed such a double piercing structure that a convex portion (indent) 10 for pushing up the flat circuit body 1 is provided on the center of the plane portion 6 of the electric connecting terminal 2, through holes 11 and 12 capable of inserting the tips of the piercing portions 7 and 8 are provided on opposite sides of the convex portion 10, and the tips of the piercing portions 7 and 8 are caused to penetrate through the flat circuit body 1 again when the piercing portions 7 and 8 penetrating through the flat circuit body 1 are to be folded.
Such a countermeasure can reduce the looseness caused by the spring back, thereby preventing the conducting reliability from being deteriorated. However, on the other hand, the clearance L2 to be maintained between the piercing portions 7 and 8 is further increased due to the double piercing process of the piercing portions 7 and 8. As a result, there is a problem in that the array pitch P1 of the conductor in the flat circuit body 1 is further increased and the size of the flat circuit body 1 is enlarged still more.
The invention has an object to solve the problems and to provide an excellent electric connecting terminal capable of enhancing conducting reliability for a flat circuit body and of reducing the width of the flat circuit body.
The object of the invention is achieved by an electric connecting terminal to be connected to a flat circuit body comprising:
a plane portion; and
a pair of piercing portions having tips erected from opposite side edges of the plane portion,
wherein the tips penetrate through a coating and a conductor of the flat circuit body and is folded in such a direction as to approach each other, and
wherein one of the tips penetrating through the flat circuit body is inverted toward the plane portion to pierce the conductor and the other tip is superposed on the one of the tips for urging the one of the tips toward the plane portion.
According to the structure, when a pair of piercing portions to pierce the flat circuit body are to penetrate through the flat circuit body and to be folded, the tip of one of the piercing portions is superposed on that of the other piercing portion. Therefore, only the occupied width of almost one of the piercing portions is enough for the occupied width of the piercing portions.
As compared with a conventional electric connecting terminal in which the piercing portions individually require the occupied widths and a clearance is to be provided between the piercing portions, the occupied width on the flat circuit body of one electric connecting terminal can be reduced considerably and the array pitch of the conductor on the flat circuit body can be reduced.
Moreover, the tip of one of the piercing portions to be folded earlier after penetrating through the flat circuit body is brought into such a state as to pierce the conductor of the flat circuit body again and is pressed by the tip of the other piercing portion. Therefore, it is possible to control the spring back of one of the piercing portions through the tip of the other piercing portion.
Thus, the fixation of the electric connecting terminal to the flat circuit body can be prevented from being loosened by the spring back and the conducting reliability for the flat circuit body can also be enhanced.
It is preferable that the plane portion should be provided with an embossed convex portion protruded toward the flat circuit body.
In this case, the flat circuit body provided on the embossed convex portion is brought into such a state as to be lifted up toward the tip of one of the piercing portions which are folded.
Therefore, the tip of one of the piercing portions which is inverted toward the plane portion side and is caused to pierce the conductor again can pierce the conductor easily in a smaller folding amount than that in the case in which the plane portion is flat.
Moreover, the embossed convex portion applies bending deformation to the conductor of the flat circuit body. Consequently, the shear plane of the conductor is pushed against the penetrating portion of each of the piercing portions so that a contact load can be increased.
Thus, the conducting reliability for the flat circuit body can further be enhanced.